Voice messaging and call waiting are well known communications services features that have enjoyed tremendous commercial success in the marketplace. Voice messaging allows a caller to record a message for an unavailable called party. By contrast, call waiting permits a called party who is already busy on a first call, to be informed that another call is waiting. The benefits of call waiting are not without some inconveniences. For example, call waiting subscribers quite often resent having to interrupt a conversation with a first party to answer a less important, if not a nuisance second call in waiting. Yet, the presumption of importance of the second call in waiting sometimes compels a called party to interrupt a first call to answer that second call. Too often the presumption is rebutted when the called party finds out--to his or her chagrin --. that the second call is an unimportant or a nuisance call.
In response to this problem, network designers have developed communications features, such as call screening or caller-identification to screen incoming calls based on a caller's telephone number or to provide identification information of a calling party to a called party. While those features sometimes assist a subscriber in deciding whether to interrupt a current call in progress to answer a second call in waiting, they represent an inadequate solution to the problem at hand for certain types of calls. For example, the caller identification feature does not help a called party to ascertain the identity of a caller who initiates a call from an originating point other than the caller's personal telephone number(s). This is because the identification information displayed to the called party does not allow the called party to associate the identification information to a particular person. Similarly, the call screening feature would typically cause calls initiated from unknown originating points, such as public telephone sets, to be blocked regardless of the importance of the call. The problem of identifying a calling party and/or the importance of a call in waiting is further complicated by the fact that even when a called party is able to associate the identification information with a particular caller, the called party does not know whether the nature of the call in waiting warrants interruption of a first call in progress.
In an attempt to find a solution to this problem, some subscribers use their answering machines as a screening device for incoming calls. In essence, the subscriber would interrupt the recording of a message to answer a call only if the content of the message identifies a caller to whom the subscriber wishes to communicate regarding a subject of mutual interest. As is well known in the art, the operations of an answering machine, e.g., delivery of a greeting announcement and recording of a message, are triggered when the machine receives at least one ringing tone signal from a central office switch. Unfortunately, when a call waiting subscriber is already engaged in a first call, the subscriber's answering machine does not receive the appropriate ringing tone signal to trigger the operations of the subscriber's answering machine.